Background Many studies have found an increased risk of pulmonary tuberculosis (PTB) among those with diabetes mellitus (DM). However, evidence on whether the association is bidirectional remains sparse. This study investigates DM rates among those with and without prior tuberculosis (TB) disease as well as the reverse.
Methods Data on a UK general practice population, between 2003 and 2009, were obtained from The Health Improvement Network database. A series of retrospective cohort studies were completed. Individuals were successively classified as ‘exposed’ or ‘unexposed’ to TB, PTB, extrapulmonary TB (EPTB) or DM. Multivariate negative binomial regression was used to calculate incidence rate ratios (IRR) among each exposure group for outcomes of interest (TB, PTB, EPTB or DM in turn) adjusting for plausible confounding variables (age, sex, region, Townsend quintile and smoking status). Potential confounding due to ethnicity was adjusted for using McNamee’s external method.
Results DM risk was substantially raised among individuals with a history of TB disease (IRR 5.65 (95% CI 5.19 to 6.16)), PTB (IRR 5.74 (95% CI 5.08 to 6.50)) and EPTB (IRR 4.66 (95% CI 3.94 to 5.51)) compared with those without; results were attenuated after external adjustment for ethnicity (IRR 2.33 (95% CI 2.14 to 2.53)). TB risk was raised modestly among individuals with DM (IRR 1.50 (95% CI 1.27 to 1.76)) and was attenuated slightly after adjustment for ethnicity (IRR 1.26 (95% CI 1.07 to 1.48)).
Conclusion DM risk was raised among those with previous TB disease; this finding has implications for follow-up and screening of patients with TB, who may be at high risk of developing DM or related complications.
- public health
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Contributors NU and JAC originally conceived the ideas for the manuscript. FP performed the analyses, and JAC and PH helped with analyses of confounding by ethnicity. FP wrote the first draft of the manuscript with input from JAC and PH. MP, RM, PH and NU edited and critically appraised the manuscript.
Funding This publication was made possible by NPRP grant #7-627-3-167 from the Qatar National Research Fund (a member of Qatar Foundation). The findings achieved herein are solely the responsibility of the authors. JAC is also funded by the Higher Education Funding Council for England. The funders had no role in the design, conduct or analysis of the study.
Competing interests None declared.
Patient consent Not required.
Ethics approval Data collection for THIN was approved by the South-East Multicentre Research Ethics Committee (MREC) in 2003. This individual study did not require separate ethical approval as only anonymised aggregated THIN data are used; however, it was reviewed by THIN independent scientific review committee.
Provenance and peer review Not commissioned; externally peer reviewed.
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